In reply to Niels: California is a VERY big place, with lots of climbing/bouldering areas scattered around, so if you detail your proposed itinerary I (or others) could give more specific suggestions. As others have mentioned, Bishop is great, but is far from the main population centers/tourist sites. Time of year matters as well--it gets pretty toasty in much of California during the summer. Anyway, there are some popular bouldering areas in or near both San Francisco (Indian Rock, etc. in Berkley and several areas near Palo Alto and north in Marin County) and LA (Stoney Point)--not the quality or atmosphere of Bishop but fine for some exercise, as well as in many areas in bertween, and, of course, if you are there during the warmer months, many options in the mountains (Yosemite, etc.).